Introduction

Obstructive atheroma of the left main stem (LMS) is relatively unusual as it is present in only 4% of diagnostic coronary angiograms.1 Historically, disease of the LMS has been treated with particular respect as the LMS provides blood supply to at least two-thirds of the left ventricle,2 since prognosis after diagnosis of LMS obstruction is poor without treatment and because percutaneous coronary intervention (PCI) to the LMS usually involves a major bifurcation with higher calcific and fibrotic components than atherosclerosis elsewhere in the coronary tree.3 4 These historical data and technical challenges resulted in coronary bypass grafting (CABG) being the standard treatment of LMS narrowing especially because of the excellent results achieved using the left internal mammary artery graft to the left anterior descending artery.5

Encouraging outcomes when treating the LMS with PCI in patients unsuitable for surgery and technical advances in the predictability of PCI outcome have generated interest and reconsideration of the relative merits of PCI and CABG. Four small preliminary studies6–9 were performed, but provocative data from the randomised Synergy between PCI with Taxus and Cardiac Surgery (SYNTAX) trial substudy9 provided sufficient circumstantial evidence for the initiation of two international multicentre randomised comparative trials of surgery versus PCI for LMS disease: Evaluation of Xience Versus CABG for Effectiveness of Left Main …